1. Field of the Invention
The present invention relates to a solid-state image sensing device in which a plurality of pixels having photoelectric conversion elements are arranged in matrix form.
2. Related Art
Recently, CMOS image sensors have been actively developed. In particular, along with the miniaturization in a semiconductor process (reduction in design rules), a single-chip color image sensor has been commercialized in which the number of pixels exceeds five millions at a pixel pitch of, for example, 2.0 μm.
However, the trend of the pixel miniaturization is shifting toward a level with a pixel pitch of 1.7 μm and an aperture area or 1 μm or less. In such a pixel size, the wave nature of incident light is predominant, and the amount of the incident light more rapidly decreases than the reduction ratio of a pixel area due to a diffraction phenomenon. There is thus a need for new measures to increase the SN ratio of an element.
The CMOS image sensor of this kind generally has a color filter of a Bayer arrangement in which there are arranged one red (R) pixel, one blue (B) pixel and diagonal two green (G) pixels in a pixel block composed of two rows and two columns. The reason that two G pixels are provided in the pixel block is that the human visibility to green is high, and the green pixels are used as pixels for acquiring luminance (brightness) information.
Since the image quality changes depending on the arrangement of the color filter as described above, there have been proposed various techniques of elaborating the arrangement of the color filter to improve the image quality (e.g., refer to JP-A 2004-304706 (kokai), JP-A 2003-318375 (kokai) and JP-A 8-23542 (kokai)).
For example, JP-A 2004-304706 (kokai) discloses a technique in which white pixels used as luminance signals are arranged vertically and horizontally around a green pixel in order to ensure the charge quantity of the luminance signal. However, JP-A 2004-304706 (kokai) does not disclose any procedure for processing white pixel data, and gives no consideration to the processing of a pixel signal corresponding to an edge having rapidly changing luminance such as a subject at a high spatial frequency. JP-A 2003-318375 (kokai) and JP-A 8-23542 (kokai) provide no disclosure and suggestion regarding the processing of the edge either.